On the Electrical and Optical Characteristics of CdO Thin Films

Cadmium Oxide (CdO) thin films (d=0.15 µm- 0.70 µm) were deposited by thermal evaporation under vacuum onto glass substrates kept at 300 K and 473 K respectively. Depending on the substrate temperature, films with polycrystalline or amorphous structures were obtained. The influence of substrate temperature and post-deposition heat treatment on the electrical conductivity, σ, and optical transmittance in visible region was investigated. An irreversible temperature dependence of σ during heating/cooling cycles of as-grown samples was observed. The results are discussed in relation with cadmium excess and the film recystallization during annealing process. The optical energy bandgap (Eg ≅ 2.4 eV) determined from absorption spectra, indicates direct interband transitions